EP1060475B1 - Containment vessel and method for operating a condenser in a nuclear power plant - Google Patents

Description

The present invention relates to a security container a nuclear power plant with a condensation chamber, with a Pressure chamber and with one in the upper area of the pressure chamber arranged capacitor and a method of operation a capacitor in a nuclear power plant.

Modern safety concepts for nuclear power plants are just that designed to have an impact on accidents the nuclear power plant is limited and does not pollute the environment becomes. An essential point here is that for every operating situation adequate cooling of important components the nuclear power plant is guaranteed. To increase safety is provided by the emergency cooling devices provided for cooling usually designed as passive components, which are independent of external energy sources and solely due to functional by physical laws are.

From the article "SWR 1000 - The boiling water reactor of the future", Siemens Power Journal, pages 18 to 22, February 1996, Siemens AG, Germany, order no. A96001-U90-A314 an innovative construction and safety concept for a boiling water reactor known. In the boiling water reactor described therein the reactor pressure vessel is central in a safety vessel, the containment. For emergency cooling of the boiling water reactor are in the interior of the containment a closed condensation chamber and a flood basin arranged above is provided. This is too a central area open in which the reactor pressure vessel is arranged. The flood basin forms with the central area a pressure chamber. Above the flood basin, i.e. in the upper area of the pressure chamber or the containment a so-called building capacitor is arranged. The building condenser stands with a coolant refrigerator located above the containment in Connection and serves to dissipate the heat from the pressure chamber.

The efficiency of the building capacitor is sensitive on the presence of non-condensable gases, such as Nitrogen or hydrogen, the latter especially in serious accidents can occur. The non-condensable This is because gases reduce the ability of the building condenser to Heat from any present in the pressure chamber Discharge steam into the cooling basin. Hydrogen enriches due to its low specific weight upper area of the pressure chamber so that just around of the building condenser has a high concentration of non-condensable gases can be present. Because of that in this Inadequate heat dissipation via the building condenser the high concentration leads to an increase in pressure in the containment.

To remove heat from the pressure chamber in the event of an accident Concepts known in which the pressure chamber has a flow path is connected to a capacitor which in a Cooling basin is arranged, which is for example the security container. About this flow path arrives in the pressure chamber in the event of a malfunction hot steam together with the non-condensable gases the capacitor. There the steam is given off to the heat Cooling pool cooled and condensed. In the condenser a mixture of liquid and non-condensable forms Gases. So that no radioactivity gets into the environment the mixture is put back into the safety container brought in. It is usually a gas-liquid separator provided to the non-condensable gases separate. These are led into the condensation chamber and trapped there so they don't get back into the pressure chamber can exit. The liquid alternatively becomes Cooling of the reactor pressure vessel used or also passed into the condensation chamber. This is often the case Control valves used in corresponding pipes. This concept or comparable concepts for heat dissipation in the event of a malfunction are described, for example, in US Pat 5,102,617, U.S. Patent 5,149,492, U.S. Patent 5,570,401, the EP 0 681 300 A1 and EP 0 620 560 A1. All known concepts has in common that the steam to be cooled together with the non-condensable gases passed into the condenser becomes.

It is known from EP 0 492 899 A1 between the condensation chamber and provide a flow path to the pressure chamber. From a certain pressure difference between them the flow path is automatically opened to both chambers in the event of a malfunction for heat dissipation and pressure reduction Introduce steam into the condensation chamber. The flow path is designed as a U-shaped tube, the condensation tube can be designated. The two legs of the U-shaped tube are with their respective openings inside the pressure chamber or within the condensation chamber arranged. Located in the U-shaped or siphon-like bend liquid, so that through the U-shaped tube formed flow path is closed as long as the pressure in the pressure chamber is not significantly above that in the condensation chamber lies.

The present invention is based on the object Safety container of a nuclear power plant with a condenser and to provide a method of operating a capacitor, the efficiency of the capacitor being non-condensable Gases are largely unaffected.

The task aimed at the containment is carried out according to a first embodiment according to the invention solved in that the safety container is a condensation chamber, a pressure chamber and one arranged outside the pressure chamber Capacitor which communicates with the pressure chamber stands, one arranged inside the containment Discharge tube is provided which the upper area of the Fluid pressure chamber with the condensation chamber combines.

According to a second embodiment, the security container object achieved according to the invention in that that a capacitor in the interior of the containment and a discharge pipe is provided which covers the area around the Fluidic condenser with the condensation chamber connects, with the upper end of the drain pipe above the Capacitor is arranged.

The two embodiments are the jointly inventive The idea is based on a high efficiency of the capacitor to ensure by preventing non-condensable Gases in too high a concentration with the condenser in Come in contact. In principle, the capacitor can both be arranged inside and outside the pressure chamber. If it is arranged outside the pressure chamber, it will be hot steam from over the top of the pressure chamber fed a flow path. According to the first embodiment the non-condensable gases are previously Discharge pipe from the upper area of the pressure chamber into the Condensation chamber derived. At one within the Pressure chamber arranged capacitor is according to the second Embodiment provided that the non-condensable gases directly from the vicinity of the capacitor using the Discharge tube are withdrawn. The capacitor is there arranged in particular in the upper region of the pressure chamber.

Both embodiments have in common that the discharge pipe as simple tube designed and completely within the Security container is arranged. With the drain pipe an immediate and direct connection between the pressure chamber and the condensation chamber created. In the through the discharge pipe flow path are in particular no other components switched.

Due to the arrangement of the drain pipe in both Execution of the non-condensable gases specifically and on derived directly into the condensation chamber. The condensation chamber is up to a level with a Coolant filled, which is the so-called water reserve forms.

The non-condensable gases are, for example, hydrogen or inert gases such as air or nitrogen. Air or nitrogen mix comparatively in the area of the capacitor good with the steam. The ability of the capacitor to This can significantly affect heat dissipation. Because of the lower heat dissipation then the Pressure in the pressure chamber until the Steam / inert gas mixture via the discharge pipe automatically into the Condensation chamber overflows. The steam condenses there the water reserve and the non-condensable gases remain back in the gas space of the condensation chamber. The The steam / inert gas mixture flows into the condensation chamber as long as until the concentration of the non-condensable gases has decreased so far that the capacitor all supplied Can dissipate heat again.

If hydrogen is present, it collects because of its low specific weight in the upper range of Pressure chamber. In the presence of a large amount of hydrogen the condenser is surrounded by hydrogen. The The efficiency of the capacitor is then significantly impaired and the heat dissipation through the condenser is low. In As a result, the presence of inert gases is comparable for increasing the pressure in the pressure chamber and for overflow almost pure hydrogen into the condensation chamber. On this way a large part of the hydrogen enters the condensation chamber directed. The condenser is after draining again mostly surrounded by steam and can dissipate the heat of the steam well. In particular due to the arrangement of the upper end of the discharge pipe Above the condenser is the hydrogen, which is because of its low specific weight in the top Area of the pressure chamber above the condenser, purposefully derived.

The non-condensable gases remain in the condensation chamber, which is largely completed compared to the pressure chamber and cannot escape into the pressure chamber. The concentration of non-condensable gases in the The area of the capacitor therefore remains small. So it is ensures that the operation of the capacitor largely is unaffected by the non-condensable gases.

An important advantage of the arrangement of the discharge pipe is in that the capacitor is structurally simple can be. In particular, its is sufficient Design heat exchange capacity for almost pure saturated steam. The heat-exchanging surface of the condenser can therefore be made simpler and smaller than when you are away of the discharge pipe. As a rule, the heat exchangers Flat tubes packed into compact heat exchanger bundles become.

Another advantage is that the entire gas space of the condensation chamber for storing the example at released hydrogen in the event of an accident stands. In the event of a malfunction, the pressure in the containment increases therefore less than in the absence of overcurrent for the hydrogen via the discharge pipe.

To a particularly simple design of the Drain pipe and maintenance-free and safe operation to allow the outflow pipe, this preferably forms a permanently open flow path. So it's not valves Sliders or similar shut-off mechanisms in the discharge pipe intended.

In an advantageous embodiment, the lower end is immersed the drain pipe into the cooling liquid of the condensation chamber on. This causes steam to condense with the non-condensable Gases through the discharge pipe into the condensation chamber is passed directly with the introduction into the condensation chamber.

In a further preferred embodiment, the lower one opens out End of the discharge pipe below a condensation pipe, for example from the pressure chamber into the condensation chamber leads into the coolant. Such condensation pipes are intended to remove large amounts of steam from the pressure chamber into the condensation chamber and condense there, so that the pressure in the pressure chamber and thus in the containment is reduced. The condensation pipe is accordingly deeper into the cooling liquid of the condensation chamber immersed as the drain pipe, and in the drain pipe is one Lower water column available than in the condensation pipe. The lower immersion depth of the discharge pipe causes small accidents with low steam discharge only over the steam outlet pipe is transferred to the condensation chamber while the much larger condensation pipes remain closed by water plugs.

The capacitor is advantageously connected to an external one Fluidically connected cooling basin. Such a capacitor is also referred to as a building capacitor. By The heat can escape from the containment into the environment of the security container. The cooling tank is especially outside of the containment arranged on this.

The on a method of operating a capacitor in a Nuclear power plant directed task is thereby according to the invention solved that non-condensable gases from the area are discharged automatically above the capacitor, so that its efficiency of non-condensable gases largely is unaffected.

Further advantageous refinements of the method are See subclaims. The same applies to the procedure the same advantages as for the security container.

An embodiment of the invention is described below the drawing explained in more detail. The only figure shows a roughly simplified and schematic section through a safety container of a boiling water reactor nuclear power plant with a cooling basin arranged above.

According to the figure is centrally in a closed security container 1, also known as containment, a reactor pressure vessel 2 is arranged. Laterally next to the reactor pressure vessel 2 are in the security container 1 as other internals a condensation chamber 4 and one above arranged flood basin 8 is provided. The flood basin 8 is open to the interior of the security container 1 upwards. The interior is also referred to as pressure chamber 6. This forms a common pressure chamber with the flood basin 8.

Condensation chamber 4 and flood basin 8 are each partially with a cooling liquid f, in particular water, up to one Level n filled. The maximum level n in the flood basin 8 is a through the upper end Overflow pipe 10 determined. The overflow pipe 10 connects this Flood basin 8 with the condensation chamber 4 and opens into the Cooling liquid f of the condensation chamber 4. If the maximum Level n is exceeded, coolant flows f from the flood basin 8 into the condensation chamber 4. The flood basin 8 is also connected via a flood line 12 connected to the reactor pressure vessel 2 and this in an emergency supply with sufficient coolant f.

The condensation chamber 4 is opposite the pressure chamber 6 largely completed. It only stands over a condensation pipe 14 with the pressure chamber 6 in connection. The Condensation tube 14 is immersed in the cooling liquid f of the condensation chamber 4 so that between the condensation chamber 4th and pressure chamber 6 no gas exchange takes place. The condensation pipe 14 is by a water plug 15, the one Water column is formed in the condensation tube 14, closed. Only in the event of an accident when the pressure in the pressure chamber 6 rises, flows over the condensation tube 14 steam for condensing into the condensation chamber 4. In the left half of the picture is in the upper area of the security container 1 and thus in the upper area of the pressure chamber 6 a capacitor 16 arranged as a building capacitor referred to as. The condenser 16 is used as a heat exchanger designed with heat exchanger tubes and stands with one Cooling basin 18 in fluid communication. The condenser 16 can in principle also outside of the containment 1 be arranged in this cooling basin 18 and via pipes with the interior of the containment, in particular be connected to the pressure chamber 6. The cooling tank 18 is outside of the security container 1 on its Lid 20 arranged. The condenser 16 takes out the heat its surroundings within the containment 1 and forwards them to the cooling basin 18. This can cause heat emitted from the security container 1 into the external environment become.

A discharge pipe is preferred in the region of the capacitor 16 22 arranged. It is essential that its upper End 24 in the upper region of the pressure chamber 6 and in particular is arranged at a level above the capacitor 16. Its lower end 26 opens into the cooling liquid f of the condensation chamber 4. The drain pipe 22 is simple and built-in tube designed an open flow path from the pressure chamber 6 into the coolant f Condensation chamber 4 forms. Here, installation-free means that no valves or other fittings or components are switched in the flow path.

The immersion depth of the discharge pipe 22 in the cooling liquid f is smaller than that of the overflow pipe 10 and that of Condensation tube 14, which has a much larger cross-sectional area than the discharge pipe 22. The lower End 26 of the discharge pipe 22 is therefore above the respective one Outlet openings 28 of the condensation tube 14 and the Overflow pipe 10 arranged.

In the event of an accident, for example when a steam line breaks in the safety container 1 and the associated Steam escapes, the temperature and pressure in the safety container rise 1 on. Via various emergency cooling devices, of which in the figure only the capacitor 16 and that Flood basin 8 with associated flood line 12 are shown, it is ensured that the final accident pressure in the containment 1 does not exceed a permissible limit. This is done primarily through cooling and condensing of steam. The plays an important role here Condenser 16, with the heat from the containment 1 can be discharged to the outside.

In the course of a malfunction, non-condensables may become possible Gases, especially hydrogen, released the in the upper area of the safety container 1, i.e. in the enrich the upper area of the pressure chamber 6. The non-condensable Gases collect in the upper area of the pressure chamber 6 and lead to an increase in the pressure in the safety container 1. Due to the arrangement of the drain pipe 22 and the increased pressure in the area of the upper At the end of 24, the existing mixture of steam and non-condensable gases via the discharge pipe 22 from the upper region of the pressure chamber 6 into the condensation chamber 4 from. The entrained steam is in the condensation chamber 4 condensed out. Through the discharge pipe 22 is therefore in the area around the capacitor 16 an accumulation of non-condensable Avoided gases for which the entire gas space in the condensation chamber 4 is available.

In principle, the non-condensable gases affect the Efficiency of the capacitor 16 by increasing the heat exchangeability of the capacitor 16 significantly reduce. In the presence of non-condensable gases, the heat exchanger can 16 significantly less heat per unit of time and area dissipate from the steam to the cooling basin 18 than at Absence of non-condensable gases. Since this from the Around the capacitor 16 can be derived, the capacitor 16 can be designed for saturated steam. So he needs to have no large and specially designed heat exchange surfaces, those in the presence of non-condensable Gases would be essential to provide adequate heat to be able to dissipate. The capacitor 16 can therefore simply compact and therefore inexpensive.

Due to the lower immersion depth of the discharge pipe 22 in Comparison to that of the condensation tube 14 is made exclusively Steam from the pressure chamber 6 in via the discharge pipe 22 the condensation chamber 4 flow as long as in the pressure chamber 6 only a slight overpressure compared to the pressure in the condensation chamber 4. Only with larger pressure differences between pressure chamber 6 and condensation chamber 4, Steam, which only occurs briefly in exceptional cases via the condensation pipe 14 into the condensation chamber 4 flow. The condensation tube 14 has a large flow cross section on and therefore allows very large amounts of steam in the shortest possible time to condense into the condensation chamber 4 to lead.

According to the present new idea will be in a security container 1 with a capacitor 16 non-condensable Gases from the effective range of the capacitor 16 via a flow path automatically derived into the condensation chamber 4. The flow path is thereby a simple discharge pipe 22 educated. The mode of operation of the discharge pipe 22 is purely passive, so no external tax interventions are necessary. The Discharge tube 22 also requires no moving components and is therefore maintenance free. Due to the arrangement of the discharge pipe 22 becomes the operability of the capacitor 16 ensures that this is designed to be structurally simple can be.

Claims (9)

1. Containment vessel (1) of a nuclear power plant having an interior space (4, 6, 8) which has a condensing chamber (4) and a pressure chamber (6), and having a condenser (16) which is arranged outside the pressure chamber (6) and communicates with the pressure chamber (6) by way of a flow path, and also having a drain pipe (22) for non-condensable gases, characterised in that the drain pipe (22) is arranged inside the interior space (4, 6, 8) and by fluid mechanics connects the upper region of the pressure chamber (6) with the condensing chamber (4).
2. Containment vessel (1) of a nuclear power plant, having an interior space (4, 6, 8) which has a condensing chamber (4), a pressure chamber (6) and a condenser (16) that is arranged in the pressure chamber (6), and also having a drain pipe (22) for non-condensable gases, characterised in that by fluid mechanics the drain pipe (22) connects the region around the condenser (16) with the condensing chamber (4), with the upper end (24) of the drain pipe (22) being arranged above the condenser (16).
3. Containment vessel (1) according to claim 1 or 2, characterised in that the drain pipe (22) forms a permanently open flow path.
4. Containment vessel according to one of claims 1 to 3, characterised in that the condensing chamber (4) contains a cooling liquid (f) into which a lower end (26) of the drain pipe (22) dips.
5. Containment vessel according to one of claims 1 to 4, characterised in that a condensing pipe (14) is provided that leads into the condensing chamber (4), with the condensing pipe (14) ending below the lower end (26) of the drain pipe (22).
6. Containment vessel according to one of claims 1 to 5, wherein by fluid mechanics the condenser (16) communicates with an external cooling basin (18).
7. Method for operating a condenser (16) in a nuclear power plant, characterised in that non-condensable gases are automatically discharged out of the region above the condenser (16).
8. Method according to claim 7, characterised in that the non-condensable gases are directed into a condensing chamber (4), in particular into a cooling liquid (f) located in the condensing chamber (4).
9. Method according to claim 7 or 8, characterised in that the non-condensable gases are directed into a cooling liquid (f) located in the condensing chamber (4), above an outlet opening (28) of a condensing pipe (14).

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